A projection type display device includes a lamp for emitting light, a projection lens for magnifying and projecting a video, and an optical component such as a DMD (Digital Micromirror Device) that forms an image according to an image signal. In the projection type display device, when it is used, heat is generated in the optical component. Continued use of the display device at a high temperature not only deteriorates display quality but also damages the optical component. Therefore, the display device is generally cooled by air.
However, the projection type display device may be used in a store environment where there is a large flow of people or an outdoor environment where there is much dust, creating a possibility that along with the cooling air, dust may enter the projection type display device. The dust that adheres to the optical component of the projection type display device deteriorates display quality and shortens a life of the optical component. To tackle this problem, a dust-proof technology of the projection type display device has been developed.
JP2006-309096A (hereinafter, Patent Literature 1) discloses a technology for preventing incursion and sticking of dust by surrounding all optical components located from a lamp exit side to a projection lens with a dust-proof wall to seal them. The optical components are completely blocked from the outside, thus exhibiting high dust-proof characteristics. However, the sealed structure prevents heat radiation, hence a problem arises in which the optical components become degraded due to temperature increase.
Patent Literature 1 further discloses a method for blowing cooling air to the part of the lamp that is projected to the outside of the dust-proof wall to cool it. This method is efficient for cooling a lamp of an extremely large temperature increase. However, in Patent Literature 1, there is no mention of cooling of components having heat such as a DMD. In a recent projection type display device that features higher brightness, temperature increases of optical components such as a DMD in addition to a lamp are large, necessitating improvement of cooling efficiency.
JP2003-241310A (Patent Literature 2) and JP2006-189549A (Patent Literature 3) disclose technologies for preventing incursion of dust and improving cooling efficiency by using cooling air dust-removed by an air filter.
However, when the air filter is used, there are problems of roughness and clogging of the air filter. When a rough air filter is used, dust having a particle size smaller than the mesh of the filter cannot be sufficiently removed and is sucked into the projection type display device. When a fine air filter is used, whereas dust having a small particle size can be collected, the dust easily causes clogging of the air filter. The clogging of the air filter makes air suction difficult, consequently reducing cooling efficiency inside the projection type display device. This necessitates cleaning or replacement of the air filter, creating a possibility that burdens on a user will increase and costs will increase.